Why the mesh get shrink with follow path
Your question was a bit misleading, you were using the follow path function, which is made for animation I suppose, when you were actually trying to duplicate your object along the curve without deformation.
Since 2.8, you can't use the Dupliframes method anymore, so here is another one:
Create a single vertex, give it an Array modifier with Constant Offset (not Relative Offset), give it a Curve modifier with the curve as Object:

Keep the single vertex object selected, go in the Properties panel &gt; Object &gt; Instancing and click on Vertices. Now select your pylon object and parent it to the vertex object, it should repeat like that (modify the pylon orientation if it's not good):

If you want the pylon to change its direction along the curve, choose a plane instead of a single vertex, and click on its Instancing &gt; Faces insteand of Vertices.
Former answer:
You must have scaled your curve, because if you go into Edit mode you'll see in the N panel that its vertices have a Mean Radius of 0.239, you need to bring it back to 1. Now your object still rotates so make it rotate 90° on the X axis.